In an electric resistance welded pipe producing process for producing a round pipe from a metal coil or strip material having a desired length, there are a preliminary step for uncoiling the metal coil to supply it to a forming step, an initial forming step to be executed by breakdown rolls, cluster rolls, and fin pass rolls, a welding step for welding edge portions of the strip material opposed to each other with high frequency for example, a finishing step for correcting roundness and straightness of the pipe by straightening rolls, and a cutting step for cutting a produced metal pipe into a predetermined length.
In the finishing step described above, an element pipe which has been welded into the round pipe is reduced in diameter to have a desired outer diameter by a sizing stand, and thereafter, a deflection or bend is straightened by a Turk's head stand thereby to obtain a straight electric resistance welded pipe. On the other hand, in case of producing a rectangular pipe from the round pipe which has been thus obtained, after a forming step for gradually flattening respective four arcs of a circumference is executed in a four-way rolls stand having a plurality of stages, finally, in a shaping step, such a Turk's head stand as disclosed in Patent Document 1 (FIG. 1) and Patent Document 2 (FIG. 6) is used to obtain the rectangular pipe.
As a representative structure, the Turk's head stand is so constructed that jacks are mounted on four corners of a housing (face plate) in a shape of a rectangular plate having a round hole in its center part, for example, and straightening rolls are disposed in an outer peripheral part of the round hole so that positional adjustment can be made with respect to the center of the housing by means of the jacks. This housing is supported in a cantilever manner at one side of a stand which is erected, and a position of the housing itself can be adjusted in a vertical direction by the jacks which are provided on the stand. Further, a position of the stands can be adjusted in a horizontal direction thereby to adjust the position of the housing in the horizontal direction.